The goals of this research project are: (1) to identify and characterize the neuronal cell groups which project to each of the intralaminar thalamic nuclei in the cat, and (2) to determine the specific nuclei or cortical regions of the cat brain which receive input from each of the intralaminar nuclei, and (3) to determine whether individual intralaminar thalamic neurons have axons which project "essentially" to one structure, such as the corpus striatum, and have "sustaining collaterals" which project to other structures, such as the cerebral cortex; or whether there are specific populations of intralaminar neurons which project to different regions. The methods of autoradiography and horseradish peroxidase (HRP) are being used to achieve these goals.